diff --git a/lib/playbot.rb b/lib/playbot.rb
index 3f9203bfe08d40aae8fff42dc238e88f46fca224..53b94113c263fe27720c8c51d9537cbe661f3ad1 100644
--- a/lib/playbot.rb
+++ b/lib/playbot.rb
@@ -3,9 +3,8 @@ require 'net/yail/irc_bot'
 
 require 'site_plugin'
 
-#
+# --
 # Add plugins folder to LOAD_PATH and subsequently require all plugins.
-#
 dir = '../plugins'
 $LOAD_PATH << dir
 Dir[File.join(dir, '*.rb')].each {|file| require File.basename(file) }
diff --git a/lib/site_plugin.rb b/lib/site_plugin.rb
index c59d975f5322f22970fe8dd826896411ed6901d1..3ac1c3856fb0437456aba29e07b2cf686331f0e2 100644
--- a/lib/site_plugin.rb
+++ b/lib/site_plugin.rb
@@ -1,3 +1,6 @@
+# Implement a plugin system.
+#
+# Each plugin have to inherite from this class and implement a can_handle?(site) method.
 class SitePlugin
     @@repository = []
 
@@ -9,7 +12,13 @@ class SitePlugin
         @@repository << target
     end
 
+    # Return the plugin that can handle a given site.
     def self.for_site(site)
         @@repository.find {|handler| handler.can_handle? site }
     end
+
+    # A place holder method. This method *must* be implemented in the subclasses.
+    def can_handle?(site)
+        raise "Method not implemented !"
+    end
 end